Carburetor



July 28, 1942.

J. LICHTENSTEIN CARBURETOR 2 Sheets-Sheet 1 Filed June 29, 1939 INLETF052 D MUTWRTING FLUID /2 A J OUTLET FOR MOTIVRTING FLU] INV EN TOR.

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LICHTENSTEI N 2,291,048 I CARBURETOR Filed June 29, 19.39 2 Sheets-Sheet2 I NV EN TOR. c/OHHN 1 ICHTENTE/N.

a ATTORNEY;

Patented July 28, 1942 Johan LichtensteimLevallois-Perret, France. as-

signoito Societe 'Generale des Carburateurs Zenith, Geneva, Switzerland,a corporation of Switzerland Application June 29, 1939, Serial No.

In France July 5, 1938 4 Claims. (01. 261-39) This invention relates toan improvement in automatic altitude correctors for internal combustionengines in which a manometric capsule controls, by means, of aservomotor, a member which regulates the richness of the combustiblemixture delivered to the engine.

It is known that these manometric capsules are relatively fragile anddelicate, also that it is difllcult to obtain a series of capsuleshaving identical mechanical characteristics, that is to say, producingthe same elongation for a given a variation in the pressure to whichthey are sub- J'ected.

An object of the invention is to decrease the fatigue experienced by themanometric capsule of an automatic altitude corrector of the kindreferred to, and also to decrease the risk of rupture of said capsule. Afurther object is to make it possible to produce'a plurality ofaltimetric correctors which will operate alike in spite of differencesin the mechanical characteristics of the individual capsules mountedtherein. 7

According to the invention the capsule of the corrector is connectedtothe pilot member 'of a servomotor and is biased by a spring. Thepressure exerted by the spring upon said capsuleis controlled by themotor member of the servomotor, which also actuates the membercontrolling the mixture richness. The servomotor remains at rest forany-given value of the pressure acting upon the capsule, but if thatpressure varies and reaches a new value the capsule elongates orcontracts correspondingly, thereby displacing the pilot member or theservomotor. The motor member of the servomotor is thereby put intomovement, and by such movement modifies the pressure exerted by thespring upon the capsule and correspondingly changes the length of thecapsule in such direction as to restore the capsule to its initiallength and the attached pilot member to its neutral position. Operationof the servomotor, and hence further movement of the motor member, isthereby arrested.

Because of the arrangement just described,'the

capsule is always brought back to its initial length irrespective ofthe. pressure to which it is subjected. It therefore is subjected onlyto such slight variations in length as are necessary to the starting ofthe servomotor. In the devices of the prior art, wherein the capsuleelongates hardening and rupture of the capsule. This disadvantage isavoided by the control structure herein disclosed.

Furthermore, the degree of deformation of a capsule which is freelydilated or contracted by means of pressure variations to which it issubiected, depends upon the elasticity of the capsule,

which. characteristic is-very diiiicult to obtain in These.

uniform degree in a series of capsules. variations in elasticity betweenindividual capsules in the known altitude correctors result in difierentoperating characteristics in altitude correctors of the same series.This difliculty is avoided by the arrangement disclosed herein, in whichthe capsule remains at substantially the samelength, thereby eliminatingthe influence oi! the elastic characteristics of the capsule upon theoperation of the device.

The description which follows, taken in connection with the appendeddrawings, given as an example, will explain the manner in which theinvention may be practiced.

Figure 1 is'a vertical elevation, partly in section, of a carburetorembodying the invention, the parts of the altitude control being in thepositions which they would assume at ground level.

Figure 2 is a vertical section of the altitude control unit with theparts inthe positions which they would assume at altitude.

Figure 3 is a partial sectional view of an alternative arrangement forcontrolling the mixture richness and is adapted to be controlled by thealtitude control unit represented in Figures 1 and 2. v

The invention is shown in Figure 1 as applied to a carburetor of anyknown design, having an induction passage A, controlled by a throttle Band having a fuel nozzle 0 discharging into a venturi D. The airentrance E to the induction passage may be controlled by a choke valveF.

The altitude correctorrepresented in Figures 1 and 2'has a capsule ilocated within a casing and contracts due to the variations in pressurep to whichit is subjected, the capsule experiences relatively greatvariations in length each time it is subjected to material pressurevariations, and

eventually these repeated length variations cause 2. The stem 3 of thecapsule is threaded into the end wall of the casing, so as to permit theinitial adjustment to be made, after which the stem may be locked inposition by known means.

The casing 2, containing the capsule i, com= municates with atmospherethrough 'a port 2@, but it may instead be connected to any othersuitable pressure to eflect the altitude correction.

The servomotor illustrated in the drawings is of the oil pressureactuated type in which the pilot member is a plunger 4 sliding in acylindrical.

sleeve 5. while the motor member comprises a it of piston 6 isconnectedv through a link II with a lever l8, pivoted at I! to the bodyof the corrector. Lever I8 is provided at its outer end with a roller 22which engages a cam surface 23 on a lever 20, which is pivoted at 2i.Surface 23, as shown, is straight but it may be of curved form in orderto obtain any desired relation between the movement of piston 6 and themovement of lever 20. The other end 24 of lever 20 operates the spring ithrough the cup member 25.

Piston 6, which is the motor member, or driven member, of theservomotor, is connected by any suitable means to the member regulatingthe mixture'richness, which may. be of any desired typ In Figure 1, themember regulating the mixture richness has been represented as a needle21 controlling theeffective cross-section of a calibrated orifice 28which meters the fuel delivered to the mixture passage of the carburetorthrough a duct 2!. The stem III of the needle 21 is slid-' ably mountedin a guide 3i formed in the cover of the float chamber 32, in thebottomof which is the calibrated fuel orifice 28. Stem ll is connectedto a floating lever 23, one end of which is pivoted to a connecting link34, which is intum connected to the piston 6 through connecting Plunger4 thereby moves towards the left and groom I of plunger 4 eflectscommunication between the cylinder 1 and the oil inlet l2 whichcommunicates with a source of oil under pres- 5 sure. The oil underpressure pushes piston 8 downwardly, against the force of spring i4,and' pivots lever ill about its axis ii. Roller 22, mounted at the endof the lever II in engagement with surface 23, tates lever 2| in aclockwise in direction. End 24 of lever 2| thereby compresses spring II,and, under the effect of this compression, plunger 4 moves towards theright, compressing capsule i. The movement of piston I ceases when,under the pressure of the spring ll,

- 5 the pilot member 4 of the servomctor has been brought to itsoriginal pomtion, in which the central part II of the plunger closes theport Ii and cuts oil! the flow of oil under pressure to cylinthe forceexerted by spring Ii balances the force link l1 and rod IS. The otherend of lever 32 is joined to a bell crank lever 35 which is operated bythe pilot means of a rod or cable 38. Needle 21 is thus coniointlyoperable by hand as well as by the automatic altitude corrector.

of the capsule i created by the decrease in the atmospheric pressureapplied to said capsule. The lengthof the capsule therefore remainssubstantially unchanged. 1

Conversely, if the altitude decreases, capsule l contracts inresponseto'the increase in atmospheric pressure acting on it and plunger 4 movestoward the right, thereby eifecting communication between the port IIand the discharge outlet by means of groove 8; Piston 6 moves upwardlyin response to the force of the spring i4,

and the movements of the piston are transmitted tolever 20, the end 24of which moves to the left and thus decreases the compression of springll.

The movement of the piston ceases when thepilot In Figure 3, the memberregulating the richness of the mixture consists in a profiled valve 31which regulates the depression transmitted to the float chamber 38 ofthe carburetor. Valve 31 regulates the effective cross-section of thecalibrated orifice 3O throughwhich the space 42, situated above the fuellevel in fioatchamber 3|, communicates with a chamber 4|, to which is'transmitted, through duct 4!, the depression obtaining in the mixturepassage of thecarburetor. Space 42 also communicates, through acallbrated orifice 43 and a duct 44, with atmosphere or with the airintake of the carburetor. Valve 3] is carried by a stem 4! which isoperated man- .ually and by the automatic altitude control, in

the same way as stem III of the mechanism shown in Figure 1. v

The operation of the mechanism is as follows: On the ground, the variousmembers ofthe automaticaltitude control occupy the pomtionsv representedin. Figure 1.'.The pilot member of member of the servomotor (plunger 4)hasreturned to the neutral position, at which time the capsule I hasrecovered its original length.

The variations in the atmospheric pressure or any other pressure whichmay be transmitted to capsule I to obtain an altitude correction) areexclusively compensated for by variations in the length of and the forceexerted by spring ll, hence the elastic characteristics of capsule I donot play any part in the functioning of the apparatus. Also,'thedeformations to which the capinitial length by the functioning of theservo'consule is-subiected are reduced to the small amounts necessaryfor the starting of the servomotorfthat is to say; for uncovering portii, the capsule being brought immediately back to its trol. The capsuleis thus but little deformed during variations in altitude, and itsfatigue and the risks of rupture are correspondingly decreased.

when the apparatus has risen from the ground 00 level to a predeterminedaltitude, the movement the servomomcupia .the neutral positioninwhichthe in part II of the plunger 4 closes port ll. Under these conditions,the. motor member (piston t) of the servomotor is at rest. If the handcontrol connected tolever'fl by cable ll (I'igura 1 and 3) occupiu theposition "normal richness," the needle 2I.(Figure 1) or valve 21 (Figure3) occupies such a position that the mixture delivered by the carburetoris of proper richness for operation onth'e ground.

If the apparatus leaves the ground to go up in altitude, the atmosphericpressure acting on capsule i decreases, and the capsule elongates.

' of. the motor member (piston I) of the servo motor has beentransmitted by means of rod l0. connecting rods i1 and 34, andlever-.33, to the stem II and needle ll (Figure l), or tostem 4'andlvalve 31 (Figure 3). The profile of needle 21 or valve 3! is suchthat at each altitude the composition of the mixture is correct when thehand controlis maintained in the position "normal richness." v v For anygiven altitude, the pilot may modify the richness of the mixture byoperating lever I! by means 'of the control ,cable a.

Piguresland2disclose,asanexample,a servo motor using oilunderpreuure asa motive iiuid, but it is clear that, as'far as the invention isconcerned, a servo motor of any type may be used. For example, one mightutilize a pressure fluid other than oil, such as air from the outlet oia supercharger delivering air to the engine. An electric servo motor mayalso be used in which, for example, the motor member of the servo motoris actuated by an electric motor through an endless screw, and the pilotmember consists of a switch or commutator placed in the circuit of theelectric motor. The invention may be readily applied to an altitudecorrector having a servo motor of this. kind. The capsule is in suchcase joined to the switch or commutator which replaces plunger d of themechanism represented in Figures 1 and 2. The motor member of the servomotor is driven by the endless screw and is connected to the deviceregulating the richness of the mixture (needle 21, Figure 1, or profiledvalve 87, Figure 3) and operates a lever such as lever 2i? representedin Figures 1 and 2, which operates the spring biasing the capsule. Theoperation is then entirely similar to that of the apparatus describedabove, and it is unnecessary to describe it further, since the nature ofthe servo motor in itself is not an essential element of the invention.

I claim: I

1. A mixture control for a charge forming device including a sealedcapsule responsive to the difi'erence in pressures acting on the insideand outside of said capsule, an element for varying the mixturerichness, and a servomotor for actuating said element comprising a motorcontrol member in alignment with said capsule and secured thereto to bedirectly actuated thereby, a driven member operatively connected to saidelement, a spring biasing said capsule, a separate 'spring biasing saiddriven member, and means connecting the driven member and the firstnamed spring for varying the pressure of said first named spring uponmovement of the driven member, said connecting means comprising a pairof pivoted levers having a cam and follower connection therebetween.

2. In' a servo motor for a carburetor altitude control having an elementfor controlling the mixture richness, a valve for controlling amotivating fluid, a movable wall adapted to be actuated by the fluid,means operatively connecting the movable wall and the element, abarometric capsule directly connected to the valve in abuttingrelation-therewith for directly actuating the valve, aspring yieldinglyresisting movement of said valve in one direction, means interconnectingsaid movable wall and the spring to vary the resisting force of thespring, and a second spring biasing the movable wall.

3. A charge forming device having an induction passage, a fuel chamber,a fuel conduit connecting said chamber with the induction passage, andan altitude control unit comprising a servomotor having a pilot memberand a motor membar, a barometric capsule operably connected to saidpilot member and biased by a spring, a sec- ,ond spring biasing saidmotor member, means sion of said spring upon movement 01' the motormember.

4. In a fluid operated servomotor for a carburetor mixture control, avalve for controlling the flow of motivating fluid, a movable wall sub-J OHAN LICHTEN STEIN.

